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06-28-2006, 01:30 PM | #21 |
RCC Supreme Contributor
I am: eric q
Join Date: Jun 2005
Location: Crawford Lake, Ontario
Radio of choice:
Turborix # of RCs: too
Feedback: 9 / 100%
Posts: 7,148
Total Props: 27
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desiderantes meliorem patriam To err is human, to moo is bovine |
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06-28-2006, 01:40 PM | #22 |
RCC Senior Contributor
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I saw a magazine article testing RXs recently and they were getting ranges out to about 4.2 miles (6.7 km)... not great reception, but reception. Reliable reception out to about 3 miles (about 5km). I've have to find the article again to quote exact numbers (it was in 3DFlyer, I believe).
The VHF radios I use get up to about 200 NM range... mainly limited by line of sight. Good thing I have a very high platform to use them from. I wonder what the output is on those? My books don't say. Sorry... totally off topic. |
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06-28-2006, 03:28 PM | #23 | |
RCC Contributor
I am: Jay C
Join Date: Mar 2005
Location: Vancouver Island,
Radio of choice:
DX18,DX7, JR XP6102 # of RCs: 14
Feedback: 1 / 100%
Posts: 316
Total Props: 0
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Quote:
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06-28-2006, 06:13 PM | #25 |
RCC Contributor
I am: Jay C
Join Date: Mar 2005
Location: Vancouver Island,
Radio of choice:
DX18,DX7, JR XP6102 # of RCs: 14
Feedback: 1 / 100%
Posts: 316
Total Props: 0
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apologies
I humbly apologise for my ignorance i hope you can forgive this alien for such a dumb short sighted mistake.
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06-28-2006, 08:29 PM | #26 | |||
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06-28-2006, 08:55 PM | #27 |
RCC Supreme Contributor
I am: eric q
Join Date: Jun 2005
Location: Crawford Lake, Ontario
Radio of choice:
Turborix # of RCs: too
Feedback: 9 / 100%
Posts: 7,148
Total Props: 27
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I take no offense, seems loads of people miss my hyperlinks.
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desiderantes meliorem patriam To err is human, to moo is bovine |
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06-29-2006, 08:55 PM | #30 |
RCC Senior Contributor
I am: Jean B
Join Date: Nov 2004
Location: Montreal (Quebec)
Radio of choice:
Futaba...Spektrum...JR # of RCs: 40+
Feedback: 25 / 100%
Posts: 713
Total Props: 0
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Crystal swapping!!!!
Greetings,
Firstly, I'm not an engineer, nor a technician nor an espert ( however slightly ) on the issue. However, a year or so ago, I had a question that I posecd on RCU and debated for over 2 weeks with the experts until the real answers were provided to my degree of expectation. The question was a very simple one, posed in lay terms and required a simple layman's answer. "By swapping crystal, what changes in the RF that requires retuning otherwise disaster may strike? Secondly, What is the FCC really concerned with that is well beyond what we do as they appear to not be concerned about our use of radio frequencies on the 72 band. Simply put, a crystal determines the frequency on which the radio operates. There is no tuning to be done there. Change a crystal and you change the frequency. The RF module is like a generator that powers ( pushes) a signal at a particular frequency (crystal) through the air to a receiver via a tube called the antenna. Every frequency requires a specific antenna length for proper transmission to maximum range There is a formula to calculate this as we RC'ers transmit on 1/4 wave length. All of our RC radios have the same antenna length. Up to now there is no problem whatsoever. Here is the hic; Using the furmula, I calculated the required antenna length for each of our 50 channels. All channels (frequencies) came out to a different number. The total difference in length of antenna from channel 11 to 60 resulted in a mere 3/8 on an inch of 267 feet on a distance of a mile. The only way to correct that was simply to have your radio RF module retuned to that specific frequency that you just swapped in to be in tune with the fixed antenna length But then would yuou ever notice that 267 feet on a mile when we do most of our flying at less than 3500 feet. When wide band was present this could have a bearing. But now, with narrow band and the quality of equipment we use... The real benefit is still for companies that hire technicians and want to keep them on their payroll all year and keep them busy. 'Marie -Anne' from Great Planes was in on this one at that time and squintly agreed that this was a reason for "retuning". With the deregulation of the RC frequencies, FCC is not really concerned about us and so is Canada as long as with do not boost the outpower of our radios. Now, that's illegal. If crystal swapping was of such concern to the government authorities, this could simply be resolved by the issuance of an order to solder these little critters in the radio and that would end the issue. Why is it mainly Futaba which makes an issue of this? What about synthetiser modules? They don't seem to be of any concern yet they transmit their signal through the same antenna. What about warranty? The only frequency identifier is a little sticker that can easily be removed with GooGone, a commercial label remover. Once that sticker is gone, there is no way to identify the original frequency of that Tx. And that goes for any radio that you buy from our prefered web sites. |
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